Air conditioning apparatus



Feb. 4, 1941. R. G. wYLb 2,230,422

AIR CONDITIONING APPARATUS Filed Aug. 7. 1937 2 sheets-sheet 1 ATTORNEY.

Feb. 4, 1941.

R. G. WYLD AIR CONDITIONING APPARATUS Filed Aug. '7. 1937 2 Sheets-Sheet 2 @Py 5am rfMPE/PAm/Pfs F A TT ORNE Y Patented Feb. 4, 1941 eINlTED srATl-:s

2,230,422 .am coNDxTloNlNG ArrAnA'rUs Reginald G. Wyld, Dayton, Ohio, assigner, by.

mesne assignments, to Chrysler Corporation, Highland Park, Mich., a corporation of, Dela- Ware Application August 7, 1937, Serial No. 157,932

'4 2 Claims.

My present invention relates to an'air conditioning apparatus, particularly relates to air ment, thereby reducing -the initial cost of the unit and making the unit less likely to fail.

In accordance with my invention I am able to obtain accurate control of conditions by utilizing a cooling coil through all of which all of the air being conditioned is passed at all times when the unit is in operation, and a part of which is removed from the circuit of the reirigerating medium in order to obtain closer control of theremoval of latent or sensible heat from the air in accordance with the existing atmospheric conditions and the desired conditions.

The objects and advantages of my invention will be more readily apparent from the following specification taken in connection with the accompanying drawings in which Fig. l setsforth a schematic view of my system; Fig. 2 is an operating chart showing the performance of a unit .having a certain size of coil connected to "a certain size of compressor and operating in accordance with my invention; and Fig.. 3 is. a chart showing the operating range of my unit, the chart being drawn in accordance with the comfort chart devised by the Harvard School of Public Health.

Fig. 1 discloses an air conditioning yunit Id which may be of any capacity and may be of any type designed to condition atmosphere in an enclosure. The unit may be so mounted asitc take air directly from the enclosure and directthe same backfinto'the enclosure, or it maybe connected thereto by ducts, and the incoming airV may consist partly of `fresh outside` air and partly of recirculated airafr'om the enclosure or may consistentirely of either.` The unit comprises an evaporatingcoil I'I so positioned across the interior of theunit .as-tc require all of the air to `pass through all `of the coil'at all times,

I3 and a condenser Il from which condensed liquid passes through liquid pipe I5 into a header I6 having a plurality of branches Il, I8. and I8. Each header feeds refrigerant to a part of the coil I I (each part being preferably approximatelyv one-third of the coil). The refrigerant then entersthe suction header 20 and returns tothe compressor byv way of the suction pipe 2 I.

The control oi my system is accomplished by means of a circuit also set forth in rschematic fashionin Fig. 1. The compressor I3 is operated 10 by a compressor motor 3B receiving power from the power lines 3| whenl connected thereto through a switch 32. The blower is driven by a blower motor 33 receiving power from the powerl lines 34 when connected thereto through a switch 15 35. The blower vmotor may be setin operation Vby closing a -manual switch 36 completing acircuit from positive side of power lines 3Q through a solenoid 31 and back to negative side of power 1':

. lines 3i, the solenoid 3l being thereby energized to hold switch 35 in closed position. The'blower' may therefore operate independently of the compressing unit so that circulation of air maybe accomplished with or- `without 'refrigeration When the blower motor is operating acircuit '-to the compressor motor controls, which is connected to the blower circuit on the'motor side p of switch 35, may be energized. 1 The compressory control circuit comprises a line 40 and 'amanuab Y switch 4I which is preferably placed in juxta- 30 position to switch 36. The line 40 leads to a sole- 'noid 42 which, when energized. holds switch .32` in closed position thereby causing the compressorto operate. Whenall conditionsare satisfactory Y the solenoid '42 will be energized butthe circuitl can be disrupted by one-or more control elements. The control circuit is completed to the vpower lines 3l through a line 43, which :leadsjto the switch element Ill of a twoposition thermostatl T1 (preferably of the'.v snap-acting .type wellknown in the art). .With-such,athermostat,.if the temperature passes beyond aset pointtoward( the high side the contact will bei engagiedalldn if the temperature epassesabelow lthe l set point the contact Tnwillwbe engaged sothatthe circuit .45 to vsolenoid 42 lmay be; completed;y through one orv l the other of parallellines onmlr; Line. leads` to the solenoid A23,70! afsolenoidyalve -22 placed in the branch Il of header I;3,,`the ;solenoidzvalve therefore vbeing. cambie, 911;..Suspendins thevowfw of Vrefrigerant into;y a `inthe-coil The parf alle! line 4S includes a-thermestat andahumidostat H. Beyond the junctionfofllines and it, there `is also placedasafety devicecr devices., schematically represented by a high pressure cut- 10.' above 80 F. the thermostatic element 0,4 will contact Ta therebyenergizing solenoid 23 to open solenoid valve 22 and admit refrigerant to all of the coil. The refrigerant is therefore evaporated into all the coil when the temperature passes 15 beyond a high limit, regardless of the vapor content of the atmosphere. If the temperature passes below 80 F. contact Ti. will be' engaged and solenoid valve 22 will close. As long as there is further demand for cooling and removal of I 30 water vapor (the temperature remaining above the low limit of 75F. and the humidity remaining above the low limit of 50% R. H.) thecompressor will continue tooperate but refrigerant will only be expanded into two-thirds or the re- 25 minder or the con red through branches n and I8. Since the condensing unit is of a definite capacity the head pressure in discharge pipe Iiil will remain constant but the back pressure in suction pipe 2| will drop. The compressor will continue to operate under such conditions until either .the temperature or the humidity passes below the low limits, or perhaps due to increasing occupancy load or outside temperature Tamay be Arefengaged thereby throwing the entire 3s coil into operation. The high pressure cut-out will stop the compressor regardlessof the atmospheric'condition's if the compressor discharges.

more refrigerant than can pass through the coil.

In Fig. 2 there is set forth a chart of capacities in which the ordinates represent tons of refrigeration and the abscissas represent suction temperatures of a certain system having a compressor of definite capacity and a coil of definite capacity. The line 50 represents the total capacity of the compressor. in tons of refrigeration when `connected to a coil creating a two inch pressure drop in the suction line. .The line 5| represents the total capacity of a twelve inch coil having a certain face area and a certain number 50 of fins and tubes having certaindimensions when 4000 C. F. M. 01' air at 80 D. B., 50% R.. H. is passed through the coil. These lines intersect at point 52 giving the total capacity of the unit as 9.55 tons of refrigeration. The line 53 gives the proportion of the compressor capacity under the conditions set forth which is devoted to sensible work or the lowering of the dry bulbtemperature of the air being treated and line 54 gives the proportion of latent work or removal of heat of vaporization from the air. It can thus be seen that directly below point 52 the points 55 and 56 give 6.14 tons sensible and'3.4l latent tons at the full capacity of the system, and that all these points are on the line representing a suction temperature of BSI/2. Line 01 gives the capacity of two-thirds of the full coil and'lines 50 and 50 give the capacities of one-half and one-third, respectively,of the coil. Line 51 crosses line 50 at point 00 giving the total load as 7.65 tons and a suction temperature of approximately 28; points 0| and 62 giving sensible and latent loads of 4.65 tons -and 3.00 tons, respectively. It can thus be seen that by reducing the effective face area of coil l I emphasis is being. given to the extraction of moisture from the air .whereas with full capacity the aim of the unit is to extract as much sensible heat as possible. Using the control limits set forth with respect to Fig. l and the capacities set forth with 'respect to Fig. 2 it can be .seen thatTn will be contacted above 80 F. and thelsystem will operate under-a total load of 9.55I tons with the ratio of latent to total at 35.7%. If the temperature dropsv below 80 F. Tr. will be contacted and the system will operate under a total load of 7.65 tons with the ratio of latent to total at 39.4%. The system will cease operating if the temperature drops below 75 F. or the humidity below 50% R. H.

Fig. 3 is based on the form of comfort chart developed by the Harvard School of Public Health in which the ordinates are wet bulb temperatures in degrees Fahrenheit, the abscissas are dry bulb temperatures in degrees Fahrenheit, and the lines runningdiagonally upward from left to right represent relative humidities for the corresponding wet and dry bulb temperatures. dash lines running diagonally downward from left to right represent effective temperatures or' lines representing conditions of equal warmth Vand physical comfort when the air movement is 5' approximately to 25 feet per minute. Under these conditions it has been determined that the summer comfort zone isobetween the limits of approximately 64 and 79, effective temperature,

and that between approximately 68 .and 74,

effective temperature, from 75% to 98% of the people will be comfortable, the ideal summer comfort line being at 71, effective temperature. Of course department stores and theatres subject to varying loads and intermittent occupancy may have a higher comfort'l line, arid when the outside temperature varies the comfort line will also vary so that it has been determined that outside temperatures of 70 D. B. to 95 D. B. should be matched by inside comfort lines of 68 E. T. to .73 E. T. Also a further'limitation is placed upon the comfort zone in that very low relative humidities cause a feeling of dryness in the throat and nostrils and very high humidities prevent rapid removal of perspiration from the clothing, resulting in a feeling of dampness. A healthy condition of vhumidity is realized between the ranges of R. H. to 70% R. H., with 50% R. H. as the ideal condition at al1 times. Accordingly the zone into which air should be brought is in any event within the limits of the summer com fort zone; in order to satisfy o ver seventy five percent of the people it should be within the range represented by 68 to 74, effective temperature; and in order tov be truly comfortable of the full coil, which means that whenever the. temperature is above line |00 Tu will be contactedy and the full coil will operate. As soon as the temperature drops below 79 D. B. the system will operate on two-thirds coil until either the temperature drops to line |0| or the-relative humidity drops to 50%. The lower limit of the unit there fore is represented by line |0| which extends from 100% to 50% R. H., then by the 50% R. H. line until line |00 is reached, and then downward along line |00. By way of example; if a unit is placed in a closed room having a certain definite load with the air at conditions represented by point A `(the temperature at 90 D. B. andthe humidity at 70% R. H.) the unit will operate l at full capacity drawing the condition of the air downward as represented by the dash line ex- The curved tending to points B and C. Theoretically the line should extend horizontally to the left and then downward along the 100% R. H. line, but any unit will perform some latent work at all times and 100% R. H. is hardly ever achieved. Point B is on `line m0 showing the limit of operation of the full coil and point C is on line IUI showing the limit of operation of the entire unit as controlled by thermostat T. Line D-E-F shows another performance curve wherein the air is brought from 86 D. B., 40% R. H. to '74 D. B., 65% R. H. and line GH shows another performance curve where the air is brought from 90 D. B., 20% R. H. to 79 D. B., 38% R. H. The lower limit line of the unit is shown as crossing the comfort line at approximately 30% R. H., then back across the comfort line at 50% R. H., then again across the comfort line at "10% R. H.; so that the lower limit of operation is as close to the summer comfort line as can be achieved with simplied controls.

Having described the preferred embodiment of my invention and the operation thereof it should be obvious to those skilled in the art that the same may assume modications in arrangement and detail, the true scope of my invention being determined by the following claims.

I claim: l n

1. An air conditioning system comprising a compressor-condenser-expander refrigeration system including a single compressor of xed capacity and a plurality of expander coils served' by said compressor and arranged in parallel with each other, an air conditioning unit comprising a cabinet and air moving means in said cabinet, said expander coils being arranged side by side as a bank of coils extending across the interior of the cabinet so that each of said expander coils is in the path vof a part only of the total stream of air moved through the unit by said air moving means and so that all of the air being treated moves through said bank of coils, a high limit thermostat arranged to open when the temperature of the air decreases below a high limit, means responsive to the .opening of said high limitthermostat to suspend the now of refrigerant through one of said expander coils whereby to reduce the number of coils having .effect in order materially to reduce the sensible heat re-v moval capacity of the system and to lower the temperature of the refrigerant leaving the remainder of the bank of coils in order to maintain the latent heat removal capacity of the system substantially constant, and a control circuit for said compressor including circmit Vcompleting means engaged by said high limit thermostat upon opening, a humidcstat and a low limit thermostat arranged in series whereby the flow of refrigerant through all of said expander' coils is suspended due to cessation of operation of said compressor if the temperature of the air drops below a predetermined low limit so that said low limit thermostat opens or if the humidity of the air becomes such as to cause said humidostat to open while said high limit thermostat is in open position.

2. An air conditioning system comprising a compresscr-condenser-expander refrigeration system including a single'compressor of fixed capacity and a plurality of expander coils served by said compressor and arranged in parallel with each other, an air conditioning unit comprising a cabinet and air moving means in said cabinet, said expander coils being arranged side by sidev as abank of coils extending across the interior of the cabinet so that each of said expander coils is in the path of a part only of the total stream of air moved through the unit by said air moving means and so that all of the air being treated moves through said bank of coils, a high limit thermostat arranged to open when the temperature of the air decreases below a high limit, means responsive to the opening of said high limit thermostat to suspend the iiow of refrigerant through one of said expander coils whereby Yto reduce .the number of coils having effect in a low limit thermostat arranged to open if thev temperature passes below a predetermined low limit, said contact, humidostat and low limit thermostat being arranged in series whereby the compressor stops operation and refrigerant ceases flowing through any of said expander coils vif either the temperature of the air passes below a V predetermined low limit or the humidity of the air passes below a predetermined low limit while said high limit thermostat is in open position.

REGINALD G. WYLD. 

